Viologen-linked porphyrin-based covalent organic framework material and preparation method and application thereof

Abstract

The invention discloses a porphyrin-based covalent organic framework material connected by viologen and its preparation method and application. It is based on 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridyl and 5,10,15,20-tetra(4-aminophenyl)porphyrin cobalt as monomers, and synthesizes the porphyrin-based covalent organic framework material connected by viologen by freezing, vacuum sealing and high temperature reaction. The material has excellent conductivity and stability, shows high catalytic activity and current density in electrocatalytic carbon dioxide reduction, and its preparation process is simple and has good application effect.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic material preparation, and in particular relates to a viologen-linked porphyrin-based covalent organic framework material and a preparation method and application thereof. Background Art

[0002] In order to solve a series of environmental problems caused by excessive CO2 emissions, accelerating the low-carbon transformation is a crucial research topic at present. Electric energy obtained from solar energy, hydropower, wind energy, geothermal energy, etc. is a renewable clean energy. Therefore, electrocatalytic technology has become a hot research topic in recent years. Electrocatalytic carbon dioxide reduction can effectively convert carbon dioxide into chemicals or fuels with high added value, thereby realizing a closed carbon cycle and solving the problems caused by excessive carbon dioxide emissions. In recent years, in order to achieve efficient CO2 reduction, people have studied and reported a large number of catalysts, including metal-based catalysts, single-atom catalysts, etc. However, these catalysts have poor conductivity, which usually leads to low CO2RR current density, limiting their application in industry; and their structure is unstable, which is prone to reconstruction and inactivation during the electrocatalytic process; the active center is unclear, leading to difficulties in characterization and mechanism research.

[0003] Covalent organic framework (COFs) materials are a new type of CO2 electroreduction catalyst. They have clear active centers, which are conducive to mechanism research. At the same time, they have a pore structure, which is conducive to the mass transfer process of CO2 and improves the contact between CO2 and the active center. However, most COFs have poor electrical conductivity, making them difficult to use in industrial applications. Based on this, the present invention designs a viologen-linked porphyrin-based covalent organic framework material, which has good electrical conductivity and stability. It is applied to CO2 electroreduction and has excellent product selectivity and high current density. Summary of the invention

[0004] The purpose of the present invention is to provide a viologen-linked porphyrin-based covalent organic framework material and a preparation method and application thereof. The porphyrin-based covalent organic framework material is used for electrocatalytic carbon dioxide reduction and has excellent catalytic activity, stability, selectivity and high current density.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A viologen-linked porphyrin-based covalent organic framework material is prepared by using 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridyl and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin cobalt as monomers through freezing, vacuum sealing and high-temperature reaction to synthesize the viologen-linked porphyrin-based covalent organic framework material.

[0007] Specifically, 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridyl and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin cobalt are used as raw materials, ethanol and water are used as solvents to form a reaction system, and after freezing and vacuum sealing, the system is reacted at 120°C for 3 days to obtain the viologen-linked porphyrin-based covalent organic framework.

[0008] Furthermore, the molar ratio of the 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridyl and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin cobalt is 2:1.

[0009] Furthermore, the volume ratio of ethanol to water in the solvent is 4:1.

[0010] Furthermore, the reaction system may be sonicated before freezing.

[0011] Furthermore, after the reaction, the product is filtered and washed with ethanol and water respectively, then Soxhlet extraction is performed with ethanol, and finally dried.

[0012] The obtained viologen-linked porphyrin-based covalent organic framework material can be used for electrocatalytic carbon dioxide reduction reaction.

[0013] The present invention has the following advantages:

[0014] The present invention uses 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridyl and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin cobalt as monomers, and synthesizes a class of porphyrin-based covalent organic framework materials connected by viologen through a vacuum tube sealing and high-temperature reaction method. The present invention forms a CN bond between viologen and porphyrin cobalt, so that the viologen monomer and the porphyrin cobalt monomer are connected into a stable network structure, which has excellent electrical conductivity, and exhibits high catalytic activity and current density in the CO2 electrocatalytic reduction reaction, and the preparation process is simple and the application effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the X-ray spectrum of Por(Co)-Vg-COF prepared in Example.

[0016] Figure 2 This is a scanning electron microscope image of Por(Co)-Vg-COF prepared in the example.

[0017] Figure 3 This is a transmission electron microscopy image of Por(Co)-Vg-COF prepared in the example.

[0018] Figure 4 This is the infrared spectrum of Por(Co)-Vg-COF prepared in Example.

[0019] Figure 5 This is the X-ray photoelectron spectrum of Co in Por(Co)-Vg-COF prepared in the example.

[0020] Figure 6 This is the conductivity diagram of Por(Co)-Vg-COF prepared in the example.

[0021] Figure 7 Graph showing the selectivity of Por(Co)-Vg-COF obtained in the example for electrocatalytic carbon dioxide reduction in an H-type electrolytic cell.

[0022] Figure 8 This is a comparison chart of the current density of the electrocatalytic carbon dioxide reduction of Por(Co)-Vg-COF and COF-366-Co obtained in the example in the H-type electrolytic cell.

[0023] Fig. 9 This is a graph showing the stability test results of the Por(Co)-Vg-COF obtained in the example for electrocatalytic carbon dioxide reduction at -0.6V in an H-type electrolytic cell.

[0024] Fig.10 Graph showing the selectivity of electrocatalytic carbon dioxide reduction of Por(Co)-Vg-COF obtained in the example in 1 M KOH electrolyte in a gas diffusion electrode.

[0025] Fig.11 This is the selectivity diagram of the electrocatalytic carbon dioxide reduction of Por(Co)-Vg-COF obtained in the example in the gas diffusion electrode under 0.06 M H2SO4 and 0.5 M K2SO4 (pH=2) electrolytes. DETAILED DESCRIPTION

[0026] A method for preparing a viologen-linked porphyrin-based covalent organic framework material comprises the following steps:

[0027] 1) 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridinium and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin cobalt were placed in a glass tube at a molar ratio of 2:1;

[0028] 2) Add a mixture of ethanol and water (4:1, v / v) into the glass tube;

[0029] 3) subjecting the glass tube to ultrasonic treatment to fully dissolve the monomer;

[0030] 4) The obtained mixed solution was frozen in liquid nitrogen, and then vacuumed using a double-row tube, and then sealed at high temperature, and after cooling, heated in a 120°C oven for 3 days;

[0031] 5) After the reaction is completed, the mixture is filtered, washed with ethanol and water respectively, extracted with ethanol, and then dried to obtain a porphyrin-based covalent organic framework material connected with viologen.

[0032] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0033] Example Preparation of Viologen-Linked Porphyrin-Based Covalent Organic Framework (Por(Co)-Vg-COF)

[0034] 1) Weigh 0.02 mmol of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin cobalt and 0.04 mmol of 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridinium and place them in a glass tube with an inner diameter of 8 mm;

[0035] 2) Add 1.6 mL of ethanol and 0.4 mL of water to the glass tube;

[0036] 3) Ultrasonicate the glass tube for 30 minutes to fully dissolve the monomer;

[0037] 4) The obtained mixed solution was frozen in liquid nitrogen, and then vacuumed using a double-row tube, and then sealed at high temperature, and after cooling, heated in a 120°C oven for 3 days;

[0038] 5) After the reaction is completed, the mixture is filtered, washed with ethanol and water respectively, extracted with ethanol for 24 hours, and then dried in a vacuum oven at 70°C to obtain a brown solid product named Por(Co)-Vg-COF.

[0039] Figure 1-Figure 4 The X-ray spectrum, scanning electron microscope, transmission electron microscope and infrared spectrum of the prepared Por(Co)-Vg-COF are shown in Figure 1. The successful synthesis of Por(Co)-Vg-COF can be proved from the figure.

[0040] Figure 5 This is the X-ray photoelectron spectrum of Co in Por(Co)-Vg-COF prepared in Example 1. Figure 5 As shown, the Co in Por(Co)-Vg-COF has a valence of +2.

[0041] Figure 6 The conductivity diagram of Por(Co)-Vg-COF prepared in Example 1. Figure 6 As shown in Figure 2, Por(Co)-Vg-COF has good electrical conductivity, with an electrical conductivity of 3.7×10 -7 S m -1 .

[0042] Application Example 1: Electrocatalytic Carbon Dioxide Reduction Reaction

[0043] Electrode preparation: Electrochemical tests were conducted in a three-electrode H-type glass electrolytic cell, which consisted of a cathode cell and an anode cell separated by a proton exchange membrane. The working electrode was prepared by dispersing a certain amount of Por(Co)-Vg-COF in 500 μL of isopropanol, adding 0.02 mL of 5% naphthol solution, and ultrasonically dispersing it. Then, 100 μL of the above mixture was dropped on a single-sided carbon paper electrode (area 1 cm 2 ), prepared by drying at room temperature, the platinum mesh is the counter electrode and the reference electrode is Ag / AgCl.

[0044] Electrochemical performance test: 70mL of 0.5mol / L KHCO3 electrolyte was filled into the electrolytic cell, the working electrode and the reference electrode were placed in the cathode cell, the counter electrode was placed in the anode cell, the device was sealed, and high-purity carbon dioxide gas was continuously introduced into the cathode cell at a ventilation rate of 30mL per minute. After the gas reached saturation (about 30 minutes of ventilation), a cyclic voltammetry scan was performed at a scanning rate of 100 mV·s -1 The scanning range is 0 to -1.2 V (all potentials expressed have been converted to the potential relative to the standard hydrogen electrode), and the number of scanning circles is 30 circles (the role of this step is to clean the catalyst surface and play a certain activation role).

[0045] The electrocatalytic carbon dioxide performance test uses a linear voltammetric curve to characterize the catalyst activity with a scan rate of 10 mV·s -1 , the scanning range is 0 to -1.2V.

[0046] 1. Performance test of electrocatalytic carbon dioxide reduction: The test was performed using the chronoamperometry from -0.6 V to -1.1 V. The generated gas products were collected after each potential lasted for 10 minutes and analyzed by gas chromatography. The results are shown in Figure 7 , 8 .

[0047] like Figure 7 , 8 As shown in the figure, Por(Co)-Vg-COF has excellent product selectivity and high current density. The current density of Por(Co)-Vg-COF for CO increases with the increase of potential, reaching -11.2 mAcm at -0.9 V. -2 , higher than that of the porphyrin-based covalent organic framework material COF-366-Co with similar structure. The excellent CO2RR performance of Por(Co)-Vg-COF highlights the effectiveness of viologen as an ETM to transfer fast electrons to the Co center.

[0048] 2. Stability test of electrocatalytic carbon dioxide reduction: At a potential of -0.6 V, the chronoamperometry method was used to test the changes in catalyst current and catalytic product selectivity for 10 h. The results are shown in Fig. 9 .

[0049] like Fig. 9 As shown, Por(Co)-Vg-COF has good stability.

[0050] Application Example 2: Reaction steps of electrocatalytic carbon dioxide reduction

[0051] Electrode preparation: Electrochemical tests were conducted in a three-electrode gas diffusion electrode electrolytic cell, which consisted of a cathode cell and an anode cell. The working electrode was prepared by dispersing a certain amount of Por(Co)-Vg-COF in 500 μL of isopropanol, adding 0.02 ml of 5% naphthol solution and ultrasonically dispersing it. Then, 100 μL of the above mixture was dropped on a single-sided carbon paper electrode (area 0.8 cm 2 ), dried at room temperature, with platinum as the counter electrode and Ag / AgCl as the reference electrode.

[0052] Electrochemical performance test: 100ml of 1mol / L KOH electrolyte was filled in the electrolytic cell, the working electrode was fixed in the cathode cell, the counter electrode was placed in the anode cell, the device was sealed, and the electrolyte was pumped into the cathode and cathode with a peristaltic pump at a flow rate of 20ml / min. High-purity carbon dioxide gas was continuously introduced into the cathode cell at a ventilation rate of 20ml / min. The electrocatalytic carbon dioxide performance test used a linear voltammetric curve to characterize the catalyst activity, and the scanning rate was 10mV·s -1 , the scanning range is 0 to -1.2V.

[0053] Selectivity test of electrocatalytic carbon dioxide reduction: The test was performed using the chronoamperometry method from -0.5V to -0.9V. The generated gas products were collected after each potential lasted for 10 minutes and analyzed by gas chromatography. The results are shown in Fig.10 .

[0054] The electrolyte solution was replaced with 0.06 M H2SO4 + 0.5 M K2SO4 solution, and the electrocatalytic reduction performance of Por(Co)-Vg-COF was tested in the same way as above. The results are shown in Fig.11 .

[0055] Fig.10 , 11 This shows that Por(Co)-Vg-COF has excellent CO2 electrocatalytic reduction performance in gas diffusion electrodes.

[0056] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. Application of a viologen-linked porphyrin-based covalent organic framework material in an electrocatalytic carbon dioxide reduction reaction, characterized in that: The viologen-connected porphyrin-based covalent organic framework material is synthesized by using 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridyl and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin cobalt as monomers through freezing, vacuum sealing, and high-temperature reaction. The molar ratio of the 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridyl and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin cobalt is 2:

1.

2. The use according to claim 1, characterized in that: The temperature of the high temperature reaction is 120° C. and the time is 3 days.

Images